The present invention relates generally to an apparatus employed in the treatment of wastewater, and, more specifically, to a weir assembly for controlling the flow of liquid from a first wastewater receptacle to a second wastewater receptacle.
In a process for treating wastewater, influent wastewater is transferred into a tank or basin where it is treated in one or more treatment cycles until it is of a quality desirable for discharge. In a settle cycle, heavier solids separate from the liquid and settle to the tank bottom while lighter solids migrate to the wastewater surface. Floatable wastewater treatment devices may also be operated in the treatment tank to induce fluid motion of the influent wastewater or, otherwise, interact with the influent wastewater. For example, to promote aerobic conditions in a react cycle, a floatable surface aerator may be operated to induce an upward flow of wastewater that is discharged into the air above the wastewater surface. Further, a floatable downflow mixer may be operated to mix aerated water into the wastewater.
When relatively clean effluent is produced in the treatment tank, it is commonly removed from a top portion of the wastewater using a decanting device such as an overflow weir. The overflow weir is typically used in conjunction with an effluent receptacle that is positioned between the weir and a discharge outlet of the tank. When desired, effluent from a main compartment of the tank may be induced to flow over the weir and into the effluent receptacle from where it is then discharged through the discharge outlet. Typically, the effluent flow over the weir and the discharge of effluent from the effluent receptacle is initiated by merely opening a valve on the discharge outlet. The discharge outlet may be connected to a holding container that is positioned downstream of the discharge outlet and maintained at an elevation below the liquid level in the wastewater tank. Alternatively, a pump may be connected to the discharge outlet and operated to draw effluent from the effluent receptacle. In some installations, the effluent receptacle is a fixed channel located inside the tank and the weir is positioned adjacent a wall of the channel that separates the channel from the main compartment of the tank. In other installations, the effluent receptacle is a collection trough on a floatable decanting apparatus that floats on the surface of the wastewater and the weir is positioned adjacent an outer upright wall and rim of the collection trough.
During the various cycles in the treatment process, the discharge outlet is normally closed such that the liquid level in the effluent receptacle is maintained at a level corresponding to the liquid level in the main compartment of the wastewater tank. In this mode, liquid does not normally flow over the weir. However, operation of the aerator or mixer can cause substantial motion on the surface of the wastewater, including wave action and turbulence. Such wastewater motion can result in untreated or partially-treated wastewater and solid particles spilling over the weir and contaminating the effluent receptacle. To reduce such risk of effluent contamination, the weir and the effluent container are normally positioned in the wastewater tank at a location far from the wastewater treatment devices.